Troubleshoot Office 365 mail flow

Exchange Online

Applies to: Exchange Online

Topic Last Modified: 2016-07-20

Can't send or receive email? Office 365 for business has several ways that can troubleshoot the issue as an admin. We recommend using the automated solutions because they are typically easier and faster than manual troubleshooting.

Problems with mail delivery can be a very frustrating for both the user and the administrator. Whether your mailboxes are hosted on-premises, in Office 365, or a combination of both, mail flow issues can occur from time to time. Luckily, the mail flow troubleshooter (requires global admin sign-in) can help you troubleshoot some of these issues if they happened in the past 7 days. For example, if you have problems sending and receiving mail or if mail is delayed in the following scenarios:

The sender’s mailbox is hosted on Office 365, and the recipient’s mailbox is outside your organization.

The sender’s mailbox is outside your organization, and the recipient’s mailbox is hosted in Office 365.

The sender’s and recipient’s mailboxes are both located in Office 365.

The sender’s mailbox is hosted in Office 365, and the recipient’s mailbox is located on an on-premise Exchange server, and both mailboxes are in the same organization.

The sender’s mailbox is hosted on an on-premise Exchange Server server and the recipient’s mailbox is hosted in Office 365, and both mailboxes are in the same organization.

To validate and troubleshoot mail flow from Office 365 to your organization’s email server (also called on-premises server), validate your connectors. You can set up and validate connectors on the connectors page in the Exchange admin center (EAC). The built-in validation tests that your mail flow from Office 365 reaches: